The present invention relates to membrane filtration modules and a filtration cartridge that are more sanitary and are easier to replace and install than presently available filtration modules. More particularly, the present invention relates to a filtration cartridge and membrane filtration modules formed from a filtration cartridge, a reusable bowl, a reusable manifold and a reusable connecting device to connect the filtration cartridge, retaining bowl and manifold together.
The control of particulate contaminants in a filtration process such as in the semiconductor industry requires the use of ultraclean filters having membranes that remove submicron particles. It is well known that any particle that is deposited on a semiconductor wafer produces a defect when the particle is sufficiently large. Typically, in the semiconductor industry, failed defects can be produced by particles as small as about one tenth of the smallest features of the semiconductor chip. Therefore, membrane filters are used in every process step for producing semiconductor chips to purify both working liquids and gases.
Although many different designs have been developed for a filtration module used in an ultrapure liquid filtration, two designs are prevalent. In one module design, liquid to be filtered flows from one end of the filtration module to the other end. In this class of filtration modules, the feed and permeate connections are located at opposite ends of the filter thereby forcing the liquid flow to move from one end to the other. This flow configuration is referred to as an in line flow configuration. These filtration modules suffer from two disadvantages. First, they are more difficult to connect to the process equipment since the module is sandwiched between two sets of connections. Second, any free liquid remaining within the module quickly drains upon disconnection of the module because at least one connection is positioned at the bottom of the module.
A second filtration modular design locates all of the connections at the same end of the module. In this type of module, the feed and permeate ports are typically horizontally oriented at the top of “head” end of the module on opposite sides thereof. Due to their shape, these modules are referred to as having a T configuration. The T configuration facilitates connection of the head to the remaining portion of the filtration module comprising the bowl and the filtration cartridge positioned within the bowl. In this design, the bowl and filtration cartridge comprise separate elements. Thus, when constructing the filtration module, the filtration cartridge and the bowl are separately secured to and sealed to the manifold head. In addition, upon completion of filtration, the bowl and cartridge are separately removed from the head. This separate removal requires that the bowl be moved a distance substantially greater than the entire length of the cartridge thereby exposing the cartridge to permit its removal. Thereafter, the exposed cartridge is removed by hand or with a hand tool. Since the filter cartridge is saturated with the liquid being filtered which is often times corrosive or toxic, the cartridge removal step presents a danger to the worker. In addition, since the bowl must be moved the length of the cartridge, the space within which the bowl and cartridge are positioned must accommodate this removal step.
It has been proposed in U.S. Pat. No. 5,114,572, to provide a filter assembly which cooperates with a bowl to produce a filter cartridge-bowl construction which can be demounted as a single unit from a manifold. The filter cartridge is connected to the bowl by bayonet connections on the cartridge which fit into grooves within the interior surface of the bowl. The filter bowl is directly attached to the filter head by a bayonet connection that fits into slots in the head. The cartridge fits into the bowl at a position below the top of the bowl where the bowl-head connection is effected. Since the bowl is narrower at the bowl body than at the top of bowl, the bayonet connection at the narrow portion of the bowl increases blockage of fluid through the bowl.
Accordingly, it would be desirable to provide a cartridge-bowl connection which minimizes fluid blockage by positioning a cartridge-bowl connection at the top of the filter medium portion of the cartridge. In addition, it would be desirable to provide such a cartridge having a connection means which are clearly visible so that connection of the cartridge to the bowl is facilitated. Such a cartridge would promote ease of inserting the filter cartridge into the bowl, would eliminate the danger to the worker in removing the filter cartridge subsequent to filtration and would reduce the space required to install the filtration module.